In 2005 the KNDV has given the Zoology Prize to Sander van Doorn. He studied Biology in Utrecht and specialized in theoretical biology. He finished his Ph.D. with the title "Sexual Selection & Sympatric Speciation" in 2004 at the Rijksuniversiteit Groningen. He is currently working as a post-doc at the "Center for Ecological and Evolutionary of Groningen University. The following is a brief summary of his Ph.D. thesis.

Sexual Selection & Sympatric Speciation

Speciation has puzzled evolutionary biologists for centuries. Sympatric speciation is currently a major topic in the discussion around speciation. The renewed interest for this theory is understandable given several remarkable finding from modern phylogenetic research. But it is also surprising, because sympatric speciation was previously largely dismissed, as an explanation for speciation, based on mathematical models. According to the theory of sympatric speciation, speciation can occur within one population as a consequence of natural selection, without the necessity of spatial separation of populations (as is assumed by the competing theory of allopatric speciation).

Together with the degree of importance that is given to spatial separation, opinions diverge widely about the evolutionary force that drives the speciation process. Is the driving force natural selection, or random and/or unpredictable environmental events? The answer to this question is important for understanding to what degree evolution is a predictable and deterministic process.

The first part of my thesis focuses on the role of sexual selection in speciation. It is well-known that sexual selection can lead to the evolution of strong preferences of females. And that, as a consequence, males develop secondary sexual characteristics matching those preferences (e.g. peacock's tail, stickleback's red belly). This process could lead to speciation if diverging preferences occur within one population. However, in my thesis, I conclude that that such a divergence cannot occur based on the general assumptions of sexual selection models. I found that speciation though sexual selection appears to require specific biological circumstances, that are much more restrictive than previously assumed.

As it turns out, speciation through divergence of preferences can only occurs if, besides selective partner choice, competition between females and males causes strong sexual selection on secondary sexual characteristics. Therefore, I expect that speciation can only be understood as a predictable outcome of sexual selection under specific conditions. And that in many cases it will depend in spatial separation and other external factors.

Besides the general problem of speciation through sexual selection, in the second part of my thesis I focus on several processes that can enable the divergence of partner preferences, but that are still poorly understood. These "side tracks" have led to new insights in the evolution of preferences for indicators of "good genes". For example, several preferences can evolve if ornaments provide information about different fitness component, and sexual conflicts over the reliability of signals can lead to fluctuations in preferences and ornament expression. The last two chapters of the thesis deal with the evolution of behavioural conventions (winner/loser effects) that form the basis for dominance hierarchies.